Apparatus for sterile packaging



Dec. 13, 1966 W McK MARTIN APPARATUS FOR STERILE PACKAGING OriginalFiled Sept. 22, 1960 United States Patent Office 3,29l,563 Patented Dec.13, 1966 3,291,563 APPARATUS FOR STERILE PACKAGIN William McK. Martin,457 Virginia Ave., San Mateo, Calif.

Original application Sept. 22, 1960, Ser. No. 59,143, now Patent No.3,180,740, dated Apr. 27, 1965. Divided and this application Oct. 7,1964, Ser. No. 409,042

3 Claims. (Cl. 21-94) This application is a division of applicationSerial No. 59,143 liled September 22, 1960, now Patent Number 3,180,740,which is a continuation-in-part of my copending application Serial No.556,141, iiled December 29, 1955, which in turn is acontinuation-in-part of my application Serial No. 478,996, iiledDecember 31, 1954, and now abandoned.

This invention relates to process and apparatus for sterile or asepticcanning of foods -and the like.

By the terrns sterile canning and aseptic canning is meant the packagingof food products in sealed glass, metal or other containers underconditions wherein the containers and their covers or closures, arepresterilized, the food product is also presterilized, the sterile foodproduct is placed in the sterile containers, the sterile covers are thenapplied to the lilled containers, and the filling and closing operationsare carried out in a sterile atmosphere. If these precautions andconditions are observed, then it is unnecessary to post-sterilize thecanned food as by heating in a retort. The process and apparatus -of theinvention, therefore, relate to prerather than poststerilization of foodproducts.

The process and apparatus of the present invention are,

of course, applicable to the sterile canning or packaging of productsother than food-s, eg., the sterile packaging or biologicalpreparations. The invention is also applicable to the sterilization ofequipment used forsterile canning.

- Several methods of sterile canning have been proposed heretofore, someof which are at present or have in the past been in commercial use, andall of wihich employ heat to sterilize the containers and covers. Onesuc'h method is described in Dunkley U.S. Patent No. 1,270,- 798hereinafter referred to as Dunkley method. The Dunkley method employssteam as a heating medium to sterilize containers and covers and tomaintain sterile conditions during the filling .and closing operations.High pressure steam is injected into the containers as they pass througha chest in which the container sterilizing, lling and closing operationsare carried out. The chest isV open to the atmosphere at Iboth ends.Hence the injected steam expands to atmospheric pressure. If the steamemployed is high pressure, dry saturated steam, it is feasible t-oachieve steam temperatures in the chest which are considerably above 212F.; e.g., temperatures of about 280 F. have been measured at the outletnozzles. Even so, it has been amply demonstrated that the Dunkley methodis not operable unless excessively long exposure times are employed. Thereason for this is that, at such temperatures resistant food spoilageorganisms ysuch as B. stearolhermophz'lus (NCA No. 1518), B. polymzxaand other resistant bacterial spores are not killed unless exposed forexcessively long periods of time.

A second .and later method is the Ball method of Ball U.S.- Patent No.2,029,303. The Ball method employs steam as the heating and sterilizingmedium but it employs high pressure, hence high temperature steam. As aconsequence of high pressure Ball must employ sealing and valving meansto permit the introduction of empty -containers and of covers and theefllux of lled, sealed containers without loss of pressure andtemperature from the system. The Ball method is operable and can be madeto accomplish sterilization in much shorter time than the Dunkleymethod. However, the valving and sealing means employed are expensiveand cumbbersome. For this and other reasons the Ball method is not adesirable method of carrying out aseptic or sterile canning.

A third method which is at present in large scale commercial use is thatof Martin Patent No. 2,549,216, hereinafter referred to :as the Doleaseptic canning system or the Dole method. This method employs steam asin the case of Dunkley and Ball, but it combines the high temperature(hence short sterilization time) o-f Ball with the desirable atmosphericpressure feature of Dunkley. This is accomplished by imparting externalsensible heat to the steam at atmospheric pressure by means of a heatexchanger, to yield dry steam at a high temperature (eg, 400 F. orhigher) and at atmospheric pressure.

Yet another method is that of my copending application Serial No.478,996, above referred to, wherein flame and/or hot combustion gasesgenerated in situ Within the sterilizing apparatus are employed. Suchmethod is referred to hereinafter as the Martin flame method.

While the latter methods (i.e., the Dole and the Martin flame methods)provide practical processes for sterile canning wherein atmosphericpressures can be employed and sterilization times are relatively short,they have, nevertheless, certain shortcomings and disadvantages, asfollows: Both these methods employ sterilizing temperatures of about 350to 500 F. That is, the containers Iand covers are heated and maintainedat such temperatures for a suiiicient time to accomplish sterilization.With ordinary tin cans employing double end seams and soldered sideseams, failure may occur, particularly at the soldered side seams andthe double end seams, by reason of softening of the `solder or sealingcompound. In the case of glass containers excessive `breakage hasoccurred because of thermal shock, as when Ihot glass containers lfromthe sterilizer are filled with relatively cool product. Also, such hightemperatures have a deleterious effect upon the sealing compound andgasket material of covers for metal and glass containers.

It is an object of the present invention to provide a means for sterilecanning which is capable of employing substantially lower temperaturesthan presently used, yet Which will effect sterilization in a short timecomparable to that of the Dole method and the Martin dame method.

It is a particular object of the present invention to provide a methodof aseptic canning whereby the temperature can be lowered substantiallyfrom that employed lby present `day .commercial methods without,however, suffering a proportionate increase in time required,preferably, with no increase in time required.

It is a further object of the present invention to provide improvementsupon the Dunkley method of sterile canning which will -obviate the timediticulty inherent in that method..

A further object is to provide means whereby atmospheric steam can beemployed as in the Dunkley process, without the necessity of longcontact periods (as in the Dunkley method) and without the necessity ofadding superbe-at to the steam.

Yet another object is to provide improvements upon high temperaturesterilization methods whereby lower temperatures may be employed withouta serious sacriice of speed and with consequent advantage with respectto container failure.

These and other objects of the invention will be apparent from theensuing description and the appended claims.

One embodiment of the invention is illustrated diagrammatically and byway of example in the figure which will be described hereinafter. y

In accordance with my present invention I preheat containers toprecondition and predispose the microorganisms which contaminate them tothe action of heat. By this I mean that the containers, prior to thetime they are subjected to heat sterilization, are subjected to asuitable conditioning treatment to render the bacteria and othermichoorganisms which it is desired to kill, more susceptible to thelethal effect of heat. Stated another way, I pretreat containers in suchmanner as to render heat sterilization more efficient. I then subjectthe pretreated containers to sterilizing heat but under milder condi-'tions (i.e.,l at a lower temperature and/or a shorter exposure time)than in present commercial methods.

Such pretreatment is preferably given to the covers also, although thisis optional. That is, my present invention may be applied to containerswith or without application to covers. In the latter case (noapplication to covers), the covers will be sterilized by prior orconventional methods.

Pretreatment may take any of several forms, some of which are preferredand some of which are better suited for certain conditions than others.

Preferably the containers are pretreated with an added agent which iseffective to accelerate or facilitate the lethal effect of heat onbacteria and other microorganisms. Such pretreatment may take any ofseveral forms such as the following:

(l) Application of a film yof water to the surfaces `of containers,etc.; i.e., wetting or moistening the containers, -covers or the like.Such film of water acts as a heat conductor, hence renders thermalmethods of sterilization more efficient and consequently permits the useof ya lower temperature during the thermal sterilization step. Thisprocedure wets `bacterial spores, causes penetration of water into thespores, predisposes the spores to the lethal action of heat and acts asan efficient heat conductor.

(2) Pretreatment of such surfaces with a bactericidal agent such as anacid (e.g., acetic acid), an alkali, chlorine, formaldehyde, ethylalcohol, methyl alcohol or propyl alcohol, preferably in admixture withor dissolved in water or alcohol, such toxic agent being effective tokill the contaminating microorganisms or to reduce their resistance toheat and therefore render them more susceptible to being killed' by heatduring the high temperature sterilization stage. of the process. Alcoholis preferred as a bactericidal agent because of its low cost, itstoxicity tc bacteria and its lack of toxicity to human beings..

Pretreatment of such surfaces to adjust their pH to a range wherein themicroorganisms thereon are more susceptible to being killed by heat.

It will be understood that these techniques may be applied, not only tocontainers but also to covers, to processing equipment and the like. For convenience container surfaces will be referred to frequently hereinbut it will be Iunderstood that other surfaces are also contemplated.

Preferably the third method is employed, i.e., surface treatment tomodify pH. The modifying agent may be an aqueous acid solution ofsuitable pH, c g., to 4, preferably l to 3, or it may be an aqueousalkali solution of suitable pH, e.g., to 14. Suitable acids includehydrochloric, sulfuric and acetic acids, and suitable alkalis includesodium and potassium hydroxides, 5% llye solutions such as customarilyused in washing glass con-tainers in canneries, and trisodium phosphate.

Preferably the containers are treated with a surfactant solution priorto the pH modification, although surfactan-ts compati-ble with the pI-Imodifier may be used in conjunction with the pH modification, i.e., maybe incorporated in the acid or alkali solution. The advantage of using asurfactant is that it penetrates and wets contaminating materialincluding bacterial spores and renders them more accessible to the acidalkali. Examples of I also have a bactericidal effect.

suitable surfactants are alkyl benzene sulfonates (such as the Nacconalsand Oronite Detergent) and such nonionic surfactants as Antaron L-520 (atall oil-ethylene oxide polymer).

The containers are preferably sprayed with surfactant solution, thenwith acid or alkaline solution; they are preferably held in invertedposition to allow drainage of excess moisture; and the sprayedcontainers are then held for a suffi-cient time to cause the sprayedsurfaces and adhering particles and microorganisms to be thoroughlywetted and permeated. The containers, with their surfaces stll wet withacid or alkaline solution, are then subjected to heat sterilization 'byany suitable means, such as steam at 212 to 270 F. land atmosphericpressure as in the Dunkley method, steam at superatmospheric pressure asin the Ball method, superheated steam at atmospheric pressure as in theDole method or llame and combustion gases as in the Martin flame method.

The time and temperature of exposure to sterilizing heat will, ofcourse, be regulated to achieve sterilization, but it will be found thatsubstantially less rigorous conditions (eg, lower temperatures in theBall, Dole and Martin methods and shorter contact times in the Dunkleymethod) are required because of and by reason of pretreatment of thecontainers in accordance with the present invention.

It will be apparent to those skilled in the art that pretreatment inaccordance with the present invention may be carried out in a variety ofWays and by a variety of techniques. One such technique, which ispreferred, is illustrated diagrammatically in ligure to which referenceis made now.

Referring to the figure, glass or metal containers are conveyed at 10 toa twister 11 in which they are inverted so that they are upsideV downand have their open ends at the bottom. The inverted containers are thenconveyed at 12 to a preheater 13 wherein they are preheated to, say, F.This preheating step is particularly advantageous with glass containersbecause it insures amore gradual heating of the gass, thereby reducingthermal shock and breakage caused by thermal shock when the glasscontainers are heated to sterilizing temperature at a later stage in theprocess. The preheating step may, however, be omitted. The containersare next conveyed at 14 to a Washing unit 15 in which a hot cleaningsolution is sprayed onto the exterior and interior surfaces of thecontainers to wash them and remove gross impurities such as large dustparticles, grease, etc. The cleaning solution may be of any suitabletype, eg., an aqueous soap, lye, synthetic detergent or trisodiumphosphate solution. Such solutions, besides cleaning in a sanitarysense, Moreover, this washingV with solution of detergent or surfactantfacilitates subsequent wetting and penetration by the acid, alkali orbac- Itericidal agent used in the chemical pretreatment step describedhereinafter.

The Washed containers are next conducted at 16 to a steaming unit 17 inwhich they are sprayed with steam to remove excess cleaning solution bymechanical action of the steam and by condensation of steam upon thecontainer surfaces and resulting flow of condensed steam downwardly overthe container surfaces. The containers are next conveyed at 1S torinsing unit 19 wherein hot water, preferably at 20() to 210 F., issprayed onto the interior and exterior surfaces to rinse the containersthoroughly. The containers are then conveyed at 20 to a steaming unit 25in which steam jets are played onto the interior and exterior surfacesof the containers to remove adhering films or droplets of water; i.e.,to remove excess moisture.

At this stage the containers will have been thoroughly cleansed andwill, in fact, have been pretreated in accordance with one embodiment of:the invention. That is, bacterial spores, etc. will have beenthoroughly wetted and penetrated by moisture, lhence are moresusceptible to the lethal effect of heat, particularly dry heat such asused in the Dole, Dunkley and Martin methods. The containers can,therefore, be conducted directly to the high temperature sterilizationunit. However, it is preferred to continue the pretreatment by adjustingthe pH of the surfaces of the containers by spraying them with acid oralkaline solution of appropriate pH, or with a bactericidal agent suchas alcohol. This is accomplished by conducting the containers at 30 to achemical pretreating unit 31 wherein a suitable liquid is sprayed ontothe interior and exterior surfaces of the containers. Such liquid maybe, for example, an aqueous solution of acid such as acetic,hydrochloric or sulfuric acid, an aqueous solution of chlorine, anaqueous solution of an alkali such as sodium or potassium hydroxide,alcohol or formaldehyde and, in general, any chemical which isbactericidal and/ or which predisposes bacteria tothe lethal effects ofheat. Aqueous acid or alkaline solutions are preferred, the mostadvantageous being hydrochloric acid and acetic acid solutions of a pHabout 0 to 3, and a sodium hydroxide solution of pH about to 14. Thechemically pretreated containers are then conveyed at 32 to a containersterilizer 33. The latter may be of the Dunkley, all, Dole or Martintype referred to hereinabove, wherein heat is employed as thesterilizing medium. That is, the heating medium may be atmospheric steamat 212 F.-270 F., superheated high pressure steam, superheatedatmospheric stream, flame or combustion gases. It will be found thatsubstantially lower temperatures, e.g., as much as 200 F. lower, sufficein the container sterilizer 33 than are required in the prior hightemperature methods wherein containers are sterilized by dry heat butwithout pretreatment as described hereinabove. Thus, sterilizingtemperatures of 200 to 300 F may lbe employed instead of 400 to 500 F.,without corresponding increase of exposure time. Alternatively, highertemperatures (400-500 F.) but shorter exposure times may be employed.Where container failure and breakage are the chief difllculty, thetempera- .ture will be lowered, but in the case of containers and coverswhere high temperature is not a disadvantage, the exposure time may beshortened to speed up the process.

Temperatures of about 270 F. are obtainable in the Dunkley processprovided dry, saturated, high pressure steam is expanded into thecontainers. Steams at about 100 p.s.i. gauge, such as commonly used Vincanneries, is adequate for the purpose. As noted above, in the Dunkleyprocess temperatures of this order require excessive contact times. Itis a particularly impotrant advantage of the process of this inventionthat the Dunkley process is made operable with short contact times. TheDunkley process, thus modified is the preferred embodiment of thepresent invention and it avoids the necessity of adding superheat byexternal means, and the high temperatures and container failure whichcharacterize the Dole method.

The sterile containers are then conveyed at 34 to a rinsing unit 35similar to the rinsing unit 19 wherein sterile water (c g., streamcondensate) is sprayed onto the exterior and interior surfaces of thecontainers to wash the chemical fluid from the containers. This rinsing0peration may be omitted if a volatile chemical agent such as aceticacid, hydrochloric acid, formaldehyde or alcohol is used.

The sterile containers are next conveyed at 40 to a steaming unit 41similar to the steam unit 25 and are then conveyed at 42 to a twister 43wherein they are turned to upright position and are then conveyed at 44to a filler 45. Sterile product enters at 46 and the containers arefilled. The filled sterile containers are then conveyed at 47 to asealer 48. The sealer 48 is supplied with sterile covers at 49 which areapplied in the sealer to the filled con- Itainers. The sealed, sterilefilled containers are removed from the system at 50.

It will be understood, of course, that certain parts of the system willbe enclosed, although not necessarily air tight. Thus, the containersterilizer 33, the lines or conduits shown at 34, 40, 42, 44 and 47, therising unit 35, the steaming unit 41, the twister 43, the filler 45, andthe sealer 48 will be enclosed, not necessarily to prevent communicationwith the atmosphere but to provide a jacket or chest which can be keptfllled with sterile medium. Thus steam, hot combustion gases, or othersuitable sterile gas may be introduced into the enclosures of theaforesaid ducts and conveyors and units to maintain a sterile atmosphereand to `prevent ingress of nonsterile air from outside. It will also beunderstood that the covers supplied at 49 will be sterilized by the sameor some other suitable method, and that the various washing and chemicalpretreatment steps described hereinabove may be applied to the covers.

It will also be understood that the entire system, cornmencing withcontainer sterilizer 33, and including conveyor equipment, the interiorsurfaces of enclosures, etc. will be presterilized before sterilecanning is commenced. In presterilizing the equipment, any suitablemeans may be employed, e.g., superheated steam or hot combustion gases,and the time required for presterilization may be reduced by rstpretreating the equipment, `as by wetting it with water or aqueous acidsolution. A preferred method of presterilization is illustrated in thefigure.

Before describing this method of presterilization, it is desired tocomment as follows lon a modification of the present invention which isparticularly well adapted to glass containers. Referring -again to thefigure, if the. wash liquid used in the washing unit 15 is bactericidal,e.g., a 5% lye solution such as commonly used to wash glass containers,it sufllces to h-old the washed containers sufllciently long to insuresterility, -then drain them and give them a sterile rinse, then conductthe filling and closing operations under sterile conditions. Thisprocedure, which eliminates the chemical pretreatment and heatsterilization carried out at 31 and 33, is better adapted to glasscontainers than to metal containers.

Referring again to the figure, a presterilization technique is thereshown which will now be described. A volatile chemical sterilizing orbactericidal medium, e.g., an aqueous solution of acetic or hydrochloricacid of pH about 0 to 3, or an aqueous solution of formaldehyde, orethyl alcohol is maintained at 55 in a tank 56 and is pumped at ametered rate by a pump 57 through a line 58 into the inner chamber 59 ofa vaporizer 60. The vaporizer 60 has a jacket 61 providing an annularspace `62 into which high pressure steam is introduced at 63, steam andcondensate being removed through a line 64 and steam trap 65. Thetemperature of the steam jacket and the rate of flow of chemical fluidinto the chamber 59 are such that the chemical fluid is completelyvaporized and passes through lines 66 to the elements 33, 35, 41, 43, 45and 48 of the system, also, of course, into the ducts and conveyorsconnecting these elements.

The vapors of chemical fluid will condense upon the cold surfaces ofthese .elements thereby forming a film of liquid of substantially thesame composition and pH as that in the tank 56. As vapors continue toenter these elements they will heat the exposed surfaces and willsterilize them. This presterilization Aof the system is accomplished atrelatively low temperatures of the order of 200 to 250 F. This isadvantageous because higher temperatures of the order of 400 to 500 F.cause distortion of mechanical parts and cause lubrication difficulties.

It may be desirable, after presterilization has been accomplished, topass steam through the elements 33, 35, 41, 43, 45 and 48 to vaporizeand drive off the chemical medium, e.g., acetic acid, hydrochloric acid,etc.

It will, therefore, be apparent that a method and apparatus have beenprovided which, among other things, achieves sterilization ofcontainers, covers processing equipment and the like at lowertemperatures than employed in present commercial methods, such as theDole method; which renders the Dunkley method operable; and which iseffective to achieve sterile or aseptic canning at high speeds and Withfewer difficulties, such as container failure, resulting from the use ofhigh temperatures.

I claim: 1. Canning apparatus comprising la preheater for preheatingcontainers, means for washing and Water-wetting the preheatedcontainers, a container sterilizer unit employing dry heat as thesterilizing medium connected to said means for washing and Water-wettingfor treating the containers While they are still Wet, means to move saidcontainers sequentially through the preheater, the means for washing andWater-wetting and through the said sterilizer unit, means for feedingthe containers from the sterilizing unit sequentially to a ller unit andto a closing element, means for supplying sterilized covers to theclosing element, and means for maintaining sterile conditions in theller and closing element.

2. The apparatus of claim 1 having pre-sterilizing means for theapparatus, including means for volatilizing a volatile bactericidalchemical liquid and means for `distributing said Volatilized liquid insaid apparatus in association With steam in order to sterilize saidapparatus, said apparatus initially being cold, so that said volatilizedliquid and steam at iirst condense on the cold surfaces of saidapparatus, to enable sterilization at relatively low temperatures in theorder of 200 to 250 F.

3. The apparatus of claim 2 having means for sending steam alone throughthe apparatus after presterilization is accomplished to vaporize anddrive off said bactericidal liquid.

References Cited by the Examiner UNITED STATES PATENTS 1,270,798v 7/1918Dunkley 99-182 2,014,750 9/1935 Stegemann 21-80 2,549,216 471951 Martin99-182 2,761,603 4/1956 Fairchild 99;-182 X 2,771,645 11/1956 Martin99-182 2,862,821 12/1958 Wilbur et al. 99-182- 20 MORRIS O. WOLK,Primary Examiner.

F. W. BROWN, Assistant Examiner.

1. CANNING APPARATUS COMPRISING A PREHEATER FOR PREHEATING CONTAINERS,MEANS FOR WASHING AND WATER-WETTING THE PREHEATED CONTAINERS, ACONTAINER STERILIZER UNIT EMPLOYING DRY HEAT AS THE STERILIZING MEDIUMCONNECTED TO SAID MEANS FOR WASHING AND WATER-WETTING FOR TREATING THECONTAINERS WHILE THEY ARE STILL WET, MEANS TO MOVE SAID CONTAINERSSEQUENTIALLY THROUGH THE PREHEATER, THE MEANS FOR WASHING ANDWATER-WETTING AND THROUGH THE SAID STERILIZER UNIT, MEANS FOR FEEDINGTHE CONTAINERS FROM THE STERILIZING UNIT SEQUENTIALLY TO A FILLER UNITAND TO A CLOSING ELEMENT, MEANS FOR SUPPLYING STERILIZED COVERS TO THECLOSING ELEMENT, AND MEANS FOR MAINTAINING STERILE CONDITIONS IN THEFILLER AND CLOSING ELEMENT.